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public/sdk/three/jsm/shaders/ConvolutionShader.js

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+import {
+	Vector2
+} from 'three';
+
+/**
+ * Convolution shader
+ * ported from o3d sample to WebGL / GLSL
+ */
+
+const ConvolutionShader = {
+
+	name: 'ConvolutionShader',
+
+	defines: {
+
+		'KERNEL_SIZE_FLOAT': '25.0',
+		'KERNEL_SIZE_INT': '25'
+
+	},
+
+	uniforms: {
+
+		'tDiffuse': { value: null },
+		'uImageIncrement': { value: new Vector2( 0.001953125, 0.0 ) },
+		'cKernel': { value: [] }
+
+	},
+
+	vertexShader: /* glsl */`
+
+		uniform vec2 uImageIncrement;
+
+		varying vec2 vUv;
+
+		void main() {
+
+			vUv = uv - ( ( KERNEL_SIZE_FLOAT - 1.0 ) / 2.0 ) * uImageIncrement;
+			gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );
+
+		}`,
+
+	fragmentShader: /* glsl */`
+
+		uniform float cKernel[ KERNEL_SIZE_INT ];
+
+		uniform sampler2D tDiffuse;
+		uniform vec2 uImageIncrement;
+
+		varying vec2 vUv;
+
+		void main() {
+
+			vec2 imageCoord = vUv;
+			vec4 sum = vec4( 0.0, 0.0, 0.0, 0.0 );
+
+			for( int i = 0; i < KERNEL_SIZE_INT; i ++ ) {
+
+				sum += texture2D( tDiffuse, imageCoord ) * cKernel[ i ];
+				imageCoord += uImageIncrement;
+
+			}
+
+			gl_FragColor = sum;
+
+		}`,
+
+	buildKernel: function ( sigma ) {
+
+		// We lop off the sqrt(2 * pi) * sigma term, since we're going to normalize anyway.
+
+		const kMaxKernelSize = 25;
+		let kernelSize = 2 * Math.ceil( sigma * 3.0 ) + 1;
+
+		if ( kernelSize > kMaxKernelSize ) kernelSize = kMaxKernelSize;
+
+		const halfWidth = ( kernelSize - 1 ) * 0.5;
+
+		const values = new Array( kernelSize );
+		let sum = 0.0;
+		for ( let i = 0; i < kernelSize; ++ i ) {
+
+			values[ i ] = gauss( i - halfWidth, sigma );
+			sum += values[ i ];
+
+		}
+
+		// normalize the kernel
+
+		for ( let i = 0; i < kernelSize; ++ i ) values[ i ] /= sum;
+
+		return values;
+
+	}
+
+};
+
+function gauss( x, sigma ) {
+
+	return Math.exp( - ( x * x ) / ( 2.0 * sigma * sigma ) );
+
+}
+
+export { ConvolutionShader };